Rising dose of warfarin, but INR stays the same - hard to get it above 2.2

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tommyboy14

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Mar 17, 2014
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London, United Kingdom
Hi Team,

I just had my On-X valve installed on May 12th. I was on Amiodiorone unti June 18th, and now my only med is warfarin. I have started my dose out of hospital with 4mg a day, but am now up to 10mg a day. Even though the anti-coag clinic keep raising my intake, it seems very hard to get my INR consistently above 2.2.

I am otherwise fit and healthy, eat a consistent diet, no other diseases, dont drink alcohol or smoke and exercise 4-5 times per week.

The only time I managed to get INR at 2.6 since surgery is when I travelled abroad on the air plane.

Does anybody else have such problems? Is this a normal dose? Are there any tests that can be run to see if I am absorbing warfarin correctly?

I remember some people on here saying they were hyper sensitive to warfarin for genetic reasons? Is it possible to be less sensitive to warfarin for genetic reasons?

Finally, I keep getting bouts of constipation (not sure if this is a side effect of warfarin), but I didnt have them before. Is it possible that constipation and diarhea affect warfarin absorption?

If you could share your experience, I would appreciate it.

Thank you
Tommy Boy
 

Superman

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Oct 2, 2009
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Grand Rapids, MI, USA
I remember some people on here saying they were hyper sensitive to warfarin for genetic reasons? Is it possible to be less sensitive to warfarin for genetic reasons?
Yes. That’s possible. The right dose of warfarin is the one that gets you in range.

As you get farther away from surgery and alter meds, it’s not a surprise that your dose will adjust while your metabolism normalizes.

In short, you’re okay. If you don’t feel okay, definitely check with your medical team.
 

Chuck C

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Dec 5, 2020
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I have started my dose out of hospital with 4mg a day, but am now up to 10mg a day

This is totally normal and especially because you were on amiodarone upon release. My situation was similar.

I was on amiodarone upon release and it took about 3mg of warfarin to keep me in range. Range was 2.5 to 3.5 mind you. Now I take 6.75mg/day to keep in my current range of 2.0 to 3.0.

There are two reasons why it takes more warfarin now to keep in range than upon release.

One reason is that you were on amiodarone. Amiodarone interferes with the clearance of warfarin, causing the warfarin to say in your system longer and have more time to increase INR. This has been documented in several studies- see link below if interested. What this means is that it would be expected that going off of amiodarone, you would need a higher dose of warfarin to be in the same INR range.

Also, the metabolism does some adjusting during the first several months on warfarin and it usually requires a higher dose of warfarin after a few months than initially. I self test weekly and carefully track my warfarin dose. Even once I was off of amiodaron, the amount of warfarin needed to stay in range increased for several months. Compounding this, amiodarone has a very long half life- over a month, so the effects on interfering with warfarin clearance can last months, but will gradually decrease over the course of months

Is this a normal dose?

Yes, 10mg it is totally normal. If you end up needing 14mg, that would still be normal. The amount of warfarin needed to stay in range varies greatly between individuals. Some need less than 2mg/day to stay in range and others need more than 20mg/day to stay in range. The key is to focus on your own INR and how much warfarin is needed for you to stay in range and not worry that someone you know might need half that amount of warfarin to stay in range. Our metabolisms vary greatly in this area and some clear warfarin much faster than others.

Here is the link on the effect of amiodarone on INR

 

dick0236

Eat the elephant one bite at a time
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louisville, KY USA
I agree with Superman and Chuck.......10mg is no big deal and the gradual small increases by your clinic will help ensure that your INR will not "yo-yo. Your need for warfarin will eventually balance out as your body and lifestyle return to normal.
 

leadville

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Aug 28, 2017
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UK
As per the others : 10mg is normal, nothing exceptional at all.

I'm ~15mg , I'm not a big guy it's just my metabolism.

The explanation offered by Chuck is bang on the money.
 

John-3919

Member
Joined
Aug 7, 2019
Messages
18
I take 14mg per day and stay dead steady at 2.0. I’ve been on the same dose since a few weeks after my surgery 3 years ago.
 
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